Semiconductor processing methods

ABSTRACT

In one aspect, the invention includes a semiconductor processing method. An antireflective material layer is formed over a substrate. At least a portion of the antireflective material layer is annealed at a temperature of greater than about 400° C. A layer of photoresist is formed over the annealed antireflective material layer. The layer of photoresist is patterned. A portion of the antireflective material layer unmasked by the patterned layer of photoresist is removed. In another aspect, the invention includes the following semiconductor processing. An antireflective material layer is formed over a substrate. The antireflective material layer is annealed at a temperature of greater than about 400° C. A layer of photoresist is formed over the annealed antireflective material layer. Portions of the layer of photoresist are exposed to radiation waves. Some of the radiation waves are absorbed by the antireflective material during the exposing.

TECHNICAL FIELD

[0001] The invention pertains to semiconductor processing methods, suchas, for example, methods of patterning photoresist in which anantireflective material is utilized to attenuate (for example, absorb)radiation.

BACKGROUND OF THE INVENTION

[0002] Semiconductor processing frequently involves providing aphotoresist layer over a substrate. Portions of the photoresist layerare subsequently exposed to light through a masked light source. Themask contains clear and opaque features defining a pattern to be createdin the photoresist layer. Regions of the photoresist layer which areexposed to light are made either soluble or insoluble in a solvent. Ifthe exposed regions are soluble, a positive image of the mask isproduced in the photoresist. The photoresist is therefore termed apositive photoresist. On the other hand, if the non-irradiated regionsare dissolved by the solvent, a negative image results. Hence, thephotoresist is referred to as a negative photoresist.

[0003] A difficulty that can occur when exposing photoresist toradiation is that waves of radiation can propagate through thephotoresist to a layer beneath the photoresist and then be reflectedback up through the photoresist to interact with other waves propagatingthrough the photoresist. The reflected waves can constructively and/ordestructively interfere with other waves propagating through thephotoresist to create periodic variations of light intensity within thephotoresist. Such variations of light intensity can cause thephotoresist to receive non-uniform doses of energy throughout itsthickness. The non-uniform dose can decrease the accuracy and precisionwith which a masked pattern is transferred to the photoresist. Also, theradiated waves reflected back from a non-flat surface underlyingphotoresist can enter portions of the photoresist that are not supposedto be exposed. Accordingly, it is desired to develop methods whichsuppress radiation waves from being reflected by layers beneath aphotoresist layer.

[0004] A method which has been used with some success to suppressreflected waves is to form an antireflective material beneath aphotoresist layer. Antireflective materials can, for example, comprisematerials which absorb radiation, and which therefore quench reflectionof the radiation.

[0005] Antireflective materials absorb various wavelengths of radiationwith varying effectiveness. The wavelengths absorbed, and theeffectiveness with which they are absorbed, vary depending on thematerials utilized. The number of materials available for use asantireflective materials is limited. Accordingly, it is desired todevelop alternative methods of varying the wavelengths absorbed, andeffectiveness with which the wavelengths are absorbed, forantireflective materials.

SUMMARY OF THE INVENTION

[0006] In one aspect, the invention includes a semiconductor processingmethod wherein an antireflective material layer is formed over asubstrate. At least a portion of the antireflective material layer isannealed at a temperature of greater than about 400° C. A layer ofphotoresist is formed over the annealed antireflective material layer.The layer of photoresist is patterned. A portion of the antireflectivematerial layer unmasked by the patterned layer of photoresist isremoved.

[0007] In another aspect, the invention includes a semiconductorprocessing method wherein an antireflective material layer is formedover a substrate. The antireflective material layer is annealed at atemperature of greater than about 400° C. A layer of photoresist isformed over the annealed antireflective material layer. Portions of thelayer of photoresist are exposed to radiation waves, some of theradiation waves are attenuated by the antireflective material as theportions are exposed.

[0008] In yet another aspect, the invention includes a semiconductorprocessing method wherein a solid antireflective material layer isformed over a substrate. Optical properties of the antireflectivematerial layer are altered. After altering the optical properties, alayer of photoresist is formed over the antireflective material layer.Portions of the layer of photoresist are exposed to radiation waves:Some of the radiation waves are absorbed by the antireflective material.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Preferred embodiments of the invention are described below withreference to the following accompanying drawings.

[0010]FIG. 1 is a fragmentary, diagrammatic, cross-sectional view of asemiconductor wafer fragment at a preliminary processing step of amethod of the present invention.

[0011]FIG. 2 is a view of the FIG. 1 wafer fragment at a processing stepsubsequent to that shown in FIG. 1.

[0012]FIG. 3 is a view of the FIG. 1 wafer fragment at a processing stepsubsequent to that shown in FIG. 2.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] This disclosure of the invention is submitted in furtherance ofthe constitutional purposes of the U.S. Patent Laws “to promote theprogress of science and useful arts” (Article 1, Section 8).

[0014] A method of the present invention is described with reference toFIGS. 1-3. Referring to FIG. 1, a semiconductor wafer fragment 10 isillustrated at a preliminary processing step. Wafer fragment 10comprises a substrate 12, an overlying antireflective material layer 14,and a photoresist layer 16 over the antireflective material layer 14.The substrate can comprise, for example, a monocrystalline silicon waferlightly doped with a conductivity-enhancing dopant. To aid ininterpretation of this disclosure and the claims that follow, the term“semiconductive substrate” is defined to mean any constructioncomprising semiconductive material, including, but not limited to, bulksemiconductive materials such as a semiconductive wafer (either alone orin assemblies comprising other materials thereon), and semiconductivematerial layers (either alone or in assemblies comprising othermaterials). The term “substrate” refers to any supporting structure,including, but not limited to, the semiconductive substrates describedabove.

[0015] The antireflective material layer 14 can comprise an inorganicmaterial, such as, for example, a material comprising from about 5% toabout 37% (by atomic concentration) oxygen, about 10% to about 35% (byatomic concentration) nitrogen, from about 50% to about 65% (by atomicconcentration) silicon, and hydrogen. A specific example inorganicmaterial comprises about 10% (by atomic concentration) nitrogen, about25% (by atomic concentration) oxygen and about 65% (by atomicconcentration) silicon. Antireflective coating layer 14 can, forexample, consist of a single substantially homogeneous layer of theabove-described inorganic material.

[0016] As another example, antireflective coating layer 14 can comprisea stack of materials, with at least one of the materials in the stackbeing configured to attenuate radiation that passes through thephotoresist. The attenuation can encompass either total or partialabsorption of such radiation. If the attenuation encompasses onlypartial absorption, then preferably the radiation that is not absorbedwill be reflected at an appropriate wavelength and phase such that it iscancelled by other radiation passing through the stack. In an exemplaryconfiguration of an antireflective layer comprising a stack ofmaterials, the layer comprises a material comprising from about 5% toabout 37% (by atomic concentration) oxygen, about 10% to about 35% (byatomic concentration) nitrogen, from about 50% to about 65% (by atomicconcentration) silicon, and hydrogen at the bottom of the stack. Theremainder of the stack comprises one or more layers that are fully orpartially transmissive of the radiation. Such layers can comprise, forexample, silicon dioxide.

[0017] Photoresist layer 16 can comprise either a negative photoresistor a positive photoresist.

[0018] In accordance with the present invention, antireflective materiallayer 14 is applied over substrate 12 and at least a portion of layer 14is annealed at a temperature greater than about 400° C. (preferablygreater than 400° C.) prior to formation of photoresist layer 16. If theantireflective material includes a portion comprising theabove-discussed inorganic materials comprising nitrogen, oxygen,hydrogen and silicon, such portion can be applied by chemical vapordeposition at a temperature of from about 250° C. to about 400°. Theportion is then preferably annealed at a temperature of from about 800°C. to about 1050° C., more preferably from about 800° C. to about 900°C., and most preferably about 850° C. During the anneal, theantireflective material layer 14 is preferably exposed to anitrogen-containing atmosphere, such as an atmosphere comprising N₂ andAr. The atmosphere can, for example, consist essentially of N₂.

[0019] An anneal of an antireflective material layer at a temperature ofgreater than about 400° C. has been found to alter optical properties ofthe antireflective material layer to make the antireflective materiallayer more absorptive to radiation. Such anneal is particularlybeneficial for a portion of an antireflective material layer comprisingoxygen, nitrogen, silicon, and hydrogen. Specifically, the anneal hasbeen found to influence a refractive index coefficient (n) of theantireflective material layer and an extinction coefficient (energyabsorption coefficient) (k) of the antireflective material layer. Forinstance, it has been found that an anneal at greater than about 400° C.of a hydrogenated material comprising about 10% (by atomicconcentration) nitrogen, about 25% (by atomic concentration) oxygen andabout 65% (by atomic concentration) silicon will alter the “n” and “k”of the material exposed to 248 nanometer wavelength light from 2.12 and1.19, respectively, to 1.89 and 1.41, respectively. Also, the annealwill alter the “n” and “k” of such material when exposed to 365nanometer wavelength light from 2.67 and 0.59, respectively, to 2.89 and1.11, respectively.

[0020] After the anneal of at least a portion of antireflective materiallayer 14, photoresist layer 16 is formed over antireflective layer 14.Photoresist layer 16 can be formed by conventional methods. An examplemethod includes spinning a photoresist liquid over layer 14 andsubsequently volatilizing solids from the layer to form a solidphotoresist layer 16.

[0021] Referring to FIG. 2, photoresist layer 16 is patterned byexposing the layer to a patterned beam of radiation. Such patterning cancomprise conventional methods such as the negative photoresistprocessing or positive photoresist processing described in the“Background” section of this disclosure. Portions of photoresist layer16 that are exposed to the radiation will behave differently in asolvent than will portions unexposed to radiation. Either the portionexposed to radiation or the portion unexposed to radiation is removedfrom over substrate 12 to leave the other of the portions exposed toradiation or unexposed to radiation remaining over substrate 12. Whetherit is the portion that is exposed to radiation that is removed or theportion that is unexposed to radiation that is removed will depend onwhether photoresist layer 16 comprises a negative or positivephotoresist. The removal of a portion of photoresist layer 16 forms anopening 18 through photoresist layer 16. After formation of opening 18,photoresist layer 16 becomes a patterned mask. A portion ofantireflective material layer 14 is covered by the patterned mask 16,and a portion is exposed through opening 18.

[0022] During the exposure of photoresist layer 16 to radiation, some ofthe radiation penetrates through layer 16 and into antireflectivematerial layer 14. Antireflective material layer 14 attenuates, andpreferably absorbs such penetrating radiation waves.

[0023] Referring to FIG. 3, opening 18 is extended throughantireflective material layer 14 and into substrate 12. Opening 18 canbe extended by conventional methods, such as, for example, a dry plasmaetch or a wet etch.

[0024] In the shown embodiment, photoresist layer 16 is againstantireflective material layer 14. It is to be understood that in otherembodiments of the invention, which are not shown, intervening layerscan be formed between photoresist layer 16 and antireflective materiallayer 14. If such intervening layers are at least partially transparentto the radiation utilized to pattern photoresist layer 16, the radiationwill penetrate to antireflective material layer 14 and be absorbed bymaterial layer 14 during exposure of photoresist layer 16 to theradiation. It is also to be understood that if such intervening layersare present, a pattern of layer 16 could be transferred to theintervening layers without extending the pattern to layer 14. Thus, theinvention encompasses embodiments in which antireflective material layer14 is not etched.

[0025] In compliance with the statute, the invention has been describedin language more or less specific as to structural and methodicalfeatures. It is to be understood, however, that the invention is notlimited to the specific features shown and described, since the meansherein disclosed comprise preferred forms of putting the invention intoeffect. The invention is, therefore, claimed in any of its forms ormodifications within the proper scope of the appended claimsappropriately interpreted in accordance with the doctrine ofequivalents.

1. A semiconductor processing method comprising: forming anantireflective material layer over a substrate; annealing at least aportion of the antireflective material layer at a temperature of greaterthan about 400° C.; forming a layer of photoresist over the annealedantireflective material layer; patterning the layer of photoresist; andremoving a portion of the antireflective material layer unmasked by thepatterned layer of photoresist.
 2. The method of claim 1 wherein theantireflective material layer comprises a stack of layers.
 3. The methodof claim 1 wherein the antireflective material layer consists of onesubstantially homogenous layer.
 4. The method of claim 1 wherein thelayer of photoresist is formed against the antireflective materiallayer.
 5. A semiconductor processing method comprising: forming anantireflective material layer over a substrate; annealing theantireflective material layer at a temperature of greater than about400° C.; forming a layer of photoresist over the annealed antireflectivematerial layer; and exposing portions of the layer of photoresist toradiation waves, some of the radiation waves being attenuated by theantireflective material during the exposing.
 6. The method of claim 5wherein the attenuation comprises absorbing radiation waves with theantireflective coating.
 7. The method of claim 5 wherein the layer ofphotoresist is formed against the antireflective material layer.
 8. Themethod of claim 5 wherein the annealing temperature is greater thanabout 800° C.
 9. The method of claim 5 further comprising exposing theantireflective material layer to a nitrogen-containing atmosphere duringthe annealing.
 10. The method of claim 5 wherein the antireflectivematerial layer comprises oxygen, nitrogen and silicon.
 11. The method ofclaim 5 wherein the antireflective material layer comprises from about5% to about 37% (by atomic concentration) oxygen, from about 10% toabout 35% (by atomic concentration) nitrogen, from about 50% to about65% (by atomic concentration) silicon, and hydrogen.
 12. The method ofclaim 5 wherein the annealing temperature is from about 800° C. to about1050° C., and wherein the antireflective material layer comprises fromabout 5% to about 37% (by atomic concentration) oxygen, from about 10%to about 35% (by atomic concentration) nitrogen, from about 50% to about65% (by atomic concentration) silicon, and hydrogen.
 13. A semiconductorprocessing method comprising; forming a solid antireflective materiallayer over a substrate; altering optical properties of theantireflective material layer; after altering the optical properties,forming a layer of photoresist over the antireflective material layer;and exposing portions of the layer of photoresist to radiation waves andabsorbing some of the radiation waves with the antireflective material.14. The method of claim 13 further comprising exposing theantireflective material layer to an atmosphere during the altering, theatmosphere comprising at least one of nitrogen and argon.
 15. The methodof claim 13 wherein the optical properties which are altered include atleast one of an “n” coefficient or a “K” coefficient.
 16. The method ofclaim 13 wherein the altering comprises annealing the antireflectivematerial layer at a temperature greater than about 400° C.
 17. Themethod of claim 13 wherein the altering comprises annealing theantireflective material layer at a temperature greater than 800° C. 18.The method of claim 13 wherein the altering comprises annealing theantireflective material layer at a temperature of from about 800° C. toabout 1050° C., and wherein the antireflective material layer comprisesfrom about 5% to about 37% (by atomic concentration) oxygen, from about10% to about 35% (by atomic concentration) nitrogen and from about 50%to about 65% (by atomic concentration) silicon.
 19. A semiconductorprocessing method comprising; chemical vapor depositing anantireflective material layer onto a semiconductive material substrateat a temperature of from about 300° C. to about 400° C.; annealing thesolid antireflective material layer at a temperature of from about 800°C. to about 900° C. to alter at least one of an “n” coefficient or a “k”coefficient of the antireflective material layer; forming a layer ofphotoresist over the annealed antireflective material layer; exposingportions of the photoresist to radiation waves while leaving otherportions of the photoresist unexposed and absorbing some of theradiation waves with the antireflective material; and selectivelyremoving either the exposed or unexposed portions of the photoresistwhile leaving the other of the exposed and unexposed portions over thesubstrate.
 20. The method of claim 19 wherein the antireflectivematerial layer comprises oxygen, nitrogen and silicon.
 21. The method ofclaim 19 wherein the antireflective material layer comprises from about5% to about 37% (by atomic concentration) oxygen, from about 10% toabout 35% (by atomic concentration) nitrogen, from about 50% to about65% (by atomic concentration) silicon, and hydrogen.